Syndicated columnist Robert D. Novak acknowledged for the first time yesterday that he identified three confidential administration sources during testimony in the CIA leak investigation, saying he did so because they had granted him legal waivers to testify and because Special Counsel Patrick J. Fitzgerald already knew of their role.

In a column to be published today, Novak said he told Fitzgerald in early 2004 that White House senior adviser Karl Rove and then-CIA spokesman Bill Harlow had confirmed for him, at his request, information about CIA operative Valerie Plame. Novak said he also told Fitzgerald about another senior administration official who originally provided him with the information about Plame, and whose identity he says he cannot reveal even now.

"I'm still constrained as a reporter," Novak said in an interview. "It was not on the record, and he has never revealed himself as being the source, and until he does I don't feel I should."

In the column, he wrote: "I have cooperated in the investigation while trying to protect journalistic privileges under the First Amendment and shield sources who have not revealed themselves. . . . Some journalists have badgered me to disclose my role in the case. . . . I have promised to discuss my role in the investigation when permitted by the prosecution, and I do so now."

Novak triggered one of the capital's most tangled investigations with a July 2003 column reporting that Plame had suggested sending her husband, former ambassador Joseph C. Wilson IV, to Niger to investigate whether Iraqi leader Saddam Hussein was trying to obtain nuclear material from that country -- an unsupported claim that was included in President Bush's State of the Union speech. Fitzgerald, who decided last month not to pursue charges against Rove, is prosecuting I. Lewis "Scooter" Libby, a former chief of staff for Vice President Cheney, for allegedly lying to a grand jury. Judith Miller, then a New York Times reporter, went to jail for 85 days last year for initially refusing to name Libby as her source.

A mystery had swirled around Novak because he refused to say for 2 1/2 years whether he had testified while other journalists in the case -- Miller, Time magazine's Matthew Cooper, NBC's Tim Russert and, it was later disclosed, The Washington Post's Bob Woodward -- appeared before Fitzgerald, sometimes under duress.

Novak says in the forthcoming column that he initially refused to reveal his sources in an October 2003 interview with three FBI officials. He says he remained reluctant to testify before Fitzgerald, even with the waivers the three officials had given the prosecutor, but that his lawyer told him he was sure to lose a costly legal battle and be jailed for contempt of court. Novak says he testified under subpoena before a grand jury a few weeks later, in February 2004, after reading a statement about his discomfort in discussing confidential sources.

Novak said he is speaking out now because Fitzgerald notified his attorneys that the investigation, as it relates to him, has been concluded. There is no legal prohibition, however, against a witness discussing his own testimony, as other journalists in the case quickly did.

Novak's role in revealing Plame's CIA employment, which was classified, was the most controversial of his 49-year career as a Washington reporter. "What was frustrating," he said, "was that there were a lot of crazy things being said, that I had taken the Fifth Amendment or I had made a plea bargain. . . . It's obviously caused me a lot of trouble. If I had it to do all over again, would I have done it? It's a hard question to answer."

Critics say that Novak helped the administration retaliate against Wilson, who had become a prominent critic of Bush's conduct in the run-up to the Iraq war, by revealing that Wilson's wife worked for the CIA. Novak said yesterday he does not feel that he was used.

"The primary source was not a political operative," he said, and he mentioned Plame's role in the middle of a conversation about other subjects. "I don't believe it was part of a plan to discredit anybody."

A spokesman for Rove, Mark Corallo, said Novak's account of phoning Rove confirms what the White House strategist has said. "Karl never reached out to any reporters," Corallo said. "They called him."

Novak said he and Rove had differing recollections of what happened when he asked about Plame. Novak recalls Rove saying, "Oh, you know that, too?" Rove, according to Corallo, has said he responded, "I've heard that, too."

Harlow, who declined to comment yesterday, has told The Post that he challenged aspects of Novak's account three days before the column was published and warned the columnist that if he did write about Wilson's Niger trip, Plame's name should not be revealed. Novak said he has a different recollection of the conversation.

"I certainly wouldn't have used her name if anyone had indicated she might be in danger," Novak said.